False Positive 99mTc (Sn) Pyrophosphate Myocardial Infarct Images Related to Delayed Blood Pool Clearance

Three patients with atypical chest pain who were evaluated by exercise treadmill stress testing and Tc (Sn) pyrophosphate imaging had diffusely abnormal images after exercise and 24 hours later. These patients had normal exercise tests and no evidence of myocardial infarction. Repeat images several months later on each patient were again abnormal when imaged one hour after administration of the radiopharmaceutical but were normal on delayed imaging suggesting delayed blood pool clearance. Our findings suggest that a diffusely abnormal image one hour after injection may represent delayed blood pool clearance, and persistance of this abnormal image for greater than two hours after injection should be demonstrated before interpreting the study as abnormal.